1. Field of the Invention
The present invention relates generally to the field of semiconductor manufacturing. More specifically, the present invention relates to an emissivity-change-free pumping plate kit in a single wafer chamber.
2. Description of the Related Art
Chemical vapor deposition, commonly referred to as xe2x80x9cCVD,xe2x80x9d is one of a number of processes used to deposit thin layers of material on a semiconductor wafer, and may be based on thermal, plasma, or optically assisted decomposition, or reaction of chemicals. To process wafers in, for example, a thermal CVD process, a chamber is provided with a susceptor configured to receive a wafer. The wafer is typically placed onto and removed from the susceptor by a robot blade and supported by the susceptor during processing. In these typical prior art systems, the susceptor and the wafer are heated to a temperature of between 200-650xc2x0 C. prior to processing. Once the wafer is heated to an appropriate temperature, a processing fluid, typically a gas, is introduced into the chamber through a gas manifold often situated above the wafer. The processing gas thermally decomposes upon contact with the heated wafer surface to deposit a thin material layer thereon.
A primary goal of wafer processing is to obtain as many useful dies as possible from each wafer. Many factors affect the ultimate yield of die from each wafer processed. These factors include processing variables, which affect the uniformity and thickness of the material layer deposited on the wafer, and particulate contaminants that can attach to a wafer and contaminate one or more die. Both of these factors must be controlled in CVD and other processes to maximize the die yield from each wafer.
During the deposition, yellow or black powders tend to accumulate inside the chamber (e.g., on the pumping and face plates), which would cause emissivity change in the chamber and further temperature change. After processing certain number of wafers, emissivity change would render the process inconsistent from one wafer to another. Therefore, the prior art is deficient in the lack of effective means or process system that would prevent emissivity change, thereby improve the uniformity of process. Additionally, the prior art is deficient in the lack of an effective means of providing a uniform thermal boundary condition around the wafer heater so as to enhance optimal film thickness uniformity. The present invention fulfills these long-standing needs and desires in the art.
Provided herein in one aspect of the present invention is an emissivity-change-free pumping plate kit used in a single wafer chamber. This kit comprises a top open pumping plate, wherein there is no restriction to the flow. This kit may further comprise a skirt and/or a second stage choking plate. The skirt may be installed around the wafer heater, underneath the wafer heater, or along the chamber body inside the chamber, while the choking plate is installed downstream of the top open pumping plate along the purge gas flow.
The emissivity-change-free pumping plate kit disclosed herein may be used for preventing emissivity change during wafer processing by providing, in part, a gas purge to the chamber to prevent residual or powder formation on the pumping and face plates, thereby preventing an emissivity change in the chamber. More specifically, the gas purge may flow from the bottom purge or from the showerhead. Furthermore, even with a gas purge, powder formation may occur. Therefore, to reduce powder formation on the pumping and face plates, minimization of exposure to the gas is desirable, i.e., one can facilitate gas exiting between the pumping plate and face plate by using this top open pumping plate kit. The kit may also be used for providing optimal film thickness uniformity during wafer processing.
The invention further discloses a pumping plate having an aft skirt that acts to absorb heat radiated off the susceptor. The pumping plate has a wafer loading slot in the skirt that faces a wafer loading structure (slit valve) in the process chamber. Heat radiating off the susceptor, passing through the wafer loading slot in the pumping plate, enters the slit valve. The slit valve acts to absorb more heat from the susceptor than do other areas of the chamber interior. The susceptor in the area of the slit valve receives less reflected heat and as a result, the susceptor in this area can be cooler. A non-uniformly heated susceptor can effect film deposition onto the wafer and to compensate, a skirt is added to the pumping plate. The skirt is slotted, i.e. has holes to improve absorption by the skirt from heat radiating off the susceptor. The skirt reduces heat reflected back to the susceptor from the chamber walls and this has the effect of balancing the heat loss into the slit valve. With a thermally balanced susceptor, uniform film deposition onto the wafer can result.
Other and further aspects, features, and advantages of the present invention will be apparent from the following description of the embodiments of the invention given for the purpose of disclosure.